The changes in mechanical properties that occur during the plastic deformation of metals result from the complex interaction of huge numbers of mobile and immobile (trapped) line defects called dislocations. The motion and trapping of these dislocations are extremely heterogeneous and produce revealing patterns of slip lines and bands on sample surfaces. We have conducted detailed transmission electron microscopy (TEM) and in situ atomic force microscopy (AFM) studies of how these slip structures evolve on pure Al single crystals and follow-up work on Cu is underway. Such studies provide valuable qualitative and quantitative information that can be used to develop and validate fundamental deformation models. We have also used submicrometer X-ray beams at the Advanced Photon Source to directly measure the elastic strains (and thus stresses) within individual buried dislocation cell interiors and cell walls in deformed Cu single crystals, a study that settles longstanding disagreements on the presence and distribution of such strains. Many other high-impact studies are possible using techniques (both in situ and ex situ) such as TEM, AFM, SEM, and X-ray diffraction on single crystals, polycrystals, pure metals, and alloys.

 

key words

Atomic force microscopy; Dislocations; Scanning electron microscopy; Transmission electron microscopy; Work hardening; X-ray diffraction;

Citizenship:  Open to U.S. citizens

Level:  Open to Postdoctoral applicants